Stone heterogeneity index as the standard deviation of Hounsfield units: A novel predictor for shock-wave lithotripsy outcomes in ureter calculi.

Joo Yong Lee,Hae Do Jung,Jae Heon Kim,Dae Hun Lee,Doo Yong Chung,Jong Kyou Kwon,Dong Hyuk Kang,Kang Su Cho

doi:10.1038/srep23988

Abstract

We investigated whether stone heterogeneity index (SHI), which a proxy of such variations, was defined as the standard deviation of a Hounsfield unit (HU) on non-contrast computed tomography (NCCT), can be a novel predictor for shock-wave lithotripsy (SWL) outcomes in patients with ureteral stones. Medical records were obtained from the consecutive database of 1,519 patients who underwent the first session of SWL for urinary stones between 2005 and 2013. Ultimately, 604 patients with radiopaque ureteral stones were eligible for this study. Stone related variables including stone size, mean stone density (MSD), skin-to-stone distance, and SHI were obtained on NCCT. Patients were classified into the low and high SHI groups using mean SHI and compared. One-session success rate in the high SHI group was better than in the low SHI group (74.3% vs. 63.9%, P = 0.008). Multivariate logistic regression analyses revealed that smaller stone size (OR 0.889, 95% CI: 0.841–0.937, P < 0.001), lower MSD (OR 0.995, 95% CI: 0.994–0.996, P < 0.001), and higher SHI (OR 1.011, 95% CI: 1.008–1.014, P < 0.001) were independent predictors of one-session success. The radiologic heterogeneity of urinary stones or SHI was an independent predictor for SWL success in patients with ureteral calculi and a useful clinical parameter for stone fragility.

Highlights

– – – 0.567c 0.850c < 0.001c < 0.001c 0.008b 0.043b stone heterogeneity index (SHI) as the standard deviation of stone density on NCCT, and investigated whether SHI can be a novel predictor for shock-wave lithotripsy (SWL) outcomes in patients with ureteral stones
We introduced the concept of radiologic heterogeneity of a urinary stone based on a HU measurement in NCCT and demonstrated the clinical significance of SHI in the management of patients with a ureteral stone
To the best of our knowledge, this is the first report dealing with this novel clinical factor, and we revealed that SHI was an independent predictor of SWL outcomes in ureteral stones

Summary

Results

All patients were divided into low and high SHI groups according to the mean SHI. Stone size (OR 0.886, 95% CI: 0.839–0.933, P < 0.001), MSD (OR 0.996, 95% CI: 0.995–0.997, P < 0.001), and SHI (OR 1.008, 95% CI: 1.005–1.010, P < 0.001) had an independent impact on one-session stone-free status (Table 2). In patients with a stone size ≥ 10 mm, the one-session success rate was 50.2%, and SHI was significantly different between those with success and failure (279.92 ± 115.66 HU vs 204.99 ± 85.85 HU, P < 0.001). In patients with a MSD ≥ 1000 HU, SHI was significantly higher in cases with one-session success than in the cases with failure (308.02 ± 91.87 HU vs 251.48 ± 54.51 HU, P = 0.001; Table 4)

Discussion

76 Renal and ureter

Methods